I love Macadamia nuts. Two things I did not know about them; they are native to Australia, and most of the world’s population can be traced to a single Queensland tree.
Born in 1791, Allan Cunningham seemingly always had plants in his future.
His father was head gardener at Wimbledon House, in the suburbs of London, the grand residence of the Earl of Exeter. The gardens stretched for 27 hectares, and contained an artificial lake and many exotic plant specimens.
They were considered some of the finest in London.
Cunningham grew up in the grounds, often helping his father with his duties. His early experiences instilled a lifelong passion for botany.
Cunningham studied law, and worked for a time in a conveyancer’s office.
But the lure of the natural world was strong; in 1808 he resigned his position and secured a job at the Royal Botanic Gardens in Kew. Working initially as a clerk, his passion for the subject brought him to the attention of the institute’s biggest names; Robert Brown, who had sailed with Matthew Flinders, and Joseph Banks, famed in England as the botanist who had accompanied Captain Cook.
Banks took the young man under his wing, and served as his mentor. On his recommendation, Cunningham was appointed a ‘Botanical Collector’, and was duly sent out into the world to collect specimens to enhance the garden’s collection.
In 1814, Cunningham sailed to Rio De Janeiro, and spent several months studying the exotic plant life of the surrounding jungle.
Two years later, he was sent to Australia. Cunningham instantly fell in love with the country, so different to England, and would spend the next 16 years there, exploring its interior and identifying and collecting thousands of previously unknown plant and animal species.
In 1816, Cunningham joined an expedition that traversed the Blue Mountains, and explored the unknown plains to the west.
In 1817 he joined a sailing expedition that ventured up the east coast of Australia, eventually exploring Far North Queensland and the Timor Sea.
1819 saw him in Tasmania, then still called Van Dieman’s land, before a return journey to north Queensland later in the year. Another followed in 1820.
In 1822 he journeyed along the coast of Western Australia, exploring Dirk Hartog Island, Rottnest Island, and selected spots on the mainland.
Cunningham was fearless and energetic, maintaining a relentless exploration schedule through most of his time in Australia. And on his return to Sydney each time, he carefully packed up samples and specimens, to send to London by ship.
In 1828, Cunningham returned to Queensland, which had become something of a favourite area.
He travelled by ship to Moreton Bay, and then ventured south and east on horseback, exploring the MacPherson Range and the Logan River. These areas, now on the outer fringe of Brisbane, were at the time largely unknown to Europeans.
Brisbane itself had been founded only four years earlier.
They were also the lands of the Indigenous Bundjalung tribe.
Macadamia trees are from the family ‘Grevilleoideae’, and are closely related to the Banksia.
They are upright, medium sized trees, with a pale, narrow trunk, and olive green leaves. Many people are struck by their appearance. The nuts themselves are contained in a rubbery green pod, with a nub-like tip.
There are four species of Macadamia tree, all native to Australia.
In one species, the nuts contain a high level of hydrogen cyanide, and are toxic to humans. Strangely, all species are toxic to dogs; if ingested, dogs show classic signs of poisoning, symptoms including vomiting and low blood pressure.
They are the only species where this response has been recorded, and the cause is not known.
Indigenous Australians had known about Macadamia nuts for millennia.
Commonly known as ‘Kindal Kindal’, ‘Bauple’ or ‘Jindill’ in the local dialects, Macadamia trees could be found in the sub-tropical rainforest of northern New South Wales and central Queensland.
While well known, the trees were not common, and the nuts from them were considered a delicacy. They were only rarely eaten, on special occasions, and were otherwise used as gifts, especially valued when given between two different tribes.
The oil from the Macadamia tree was also used to make ceremonial body paint.
Now, Cunningham encountered the Bundjalung tribe, and made friendly relations with them. He collected specimens from their lands, to return to England.
Among these, were some examples of the Macadamia nut.
In 1847, Ferdinand von Mueller arrived in Adelaide, from Germany.
Von Mueller was a chemist who had turned to botany in his twenties, and had now come to Australia for the good of his sister’s health. His sister, Bertha, had consumption and had been urged to seek a warmer climate.
A keen naturalist, Von Mueller acquired a rural property and began exploring the Adelaide Hills, documenting the plants that he found. He submitted his findings to scientific papers, and they were widely read.
In 1851, Von Mueller moved to Melbourne, lured by the business opportunities created by the gold rush.
He worked as a chemist for a time, both on the goldfields and in the city, but his botanical expertise stood out in the growing colony. In 1853, Governor Charles La Trobe appointed Von Mueller Chief Botanist for Victoria, a post created especially for him. Four years later, he would be appointed head of the Victorian Botanic Gardens as well.
Von Mueller now followed in Alan Cunningham’s footsteps, embarking on a number of cross-country expeditions to document the local flora. He discovered more than 800 new species, and published several books on his findings.
On one of these trips, he also encountered the Macadamia.
It was Von Mueller who named the Macadamia tree; after his friend, Dr. John Macadam, the secretary of the Philosophical Institute of Australia.
Von Mueller was also the first to study the tree, and its nuts, with proper scientific rigour. Von Mueller’s colleague Walter Hill, from the Brisbane Botanic gardens, also studied the tree. Neither of them realised, at first, that the nuts were edible.
This was only discovered by accident, when Hill’s young assistant was found snacking on them.
Based on Von Mueller’s research, local farmers began to experiment with Macadamias as a commercial crop; the first plantation started in NSW in 1866.
Macadamias were brought from Queensland to Hawaii in the late 19th century.
William H. Purvis, a sugar plantation owner on Hawaii’s Big Island, returned with some seeds after a holiday in 1881. He had been taken with the look of the tree, and wanted to plant some as a wind break on his property.
Similarly, in 1892, brothers E.W. and R.A. Jordan brought seeds back from Queensland, which they planted at their home at Nu-Uanu. By this time, the Macadamia nut was becoming better known as a food item; in 1889 Australian botanist Joseph Maiden wrote, "It is well worth extensive cultivation, for the nuts are always eagerly bought.”
Still, the growth of this new industry was slow.
It was not until 1922, thirty years later, that the Hawaiian Macadamia Nut Company was established. The company planted 25 acres of Macadamia trees, which soon turned into a thriving business. Visitors to Hawaii – traders, sailors, entrepreneurs – sometimes took trees with them when they left, to try and cultivate the crop back home.
Macadamias are now grown in many places around the world.
South Africa, Hawaii and Australia are the primary producers, but there are also commercial operations in California, Costa Rica, Israel, Kenya, China, and many South American countries. Macadamias are usually propagated by grafting; a cutting is taken from an existing tree, and used to grow a new specimen. The new tree is, essentially, a clone of the original.
And this technique, has led to a remarkable consequence.
In June 2019, scientists at Australia’s Southern Cross University published the results of a study they had conducted, tracing the genetic lineage of Macadamia trees around the world. This determined that some 70% of the global population can be traced back to the trees planted by the Jordan brothers in Hawaii. These can, in turn, be traced back to Queensland, where the boys got their seeds from.
The bulk of the world’s Macadamias stem from a single Queensland tree. The descendants of this original, uber tree, still stand, on private farmland at Mooloo, near Gympie.
While extraordinary, this discovery also has a negative outcome.
The narrowness of the Macadamia’s gene pool makes it more vulnerable to factors like disease and climate change. Australian scientists are now searching for original, preferably unknown, wild variations of the tree, that they can cross breed with the Queensland variety.